Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 172106
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
306 PM MDT WED SEP 17 2014

.SHORT TERM...VALID FOR THU AND FRI...

AMPLIFIED RIDGE REMAINS OVER THE AREA THIS AFTERNOON AND WILL
PERSIST INTO THE FIRST PORTION OF THE DAY THURSDAY. PACIFIC
DISTURBANCES MOVING OVER THE RIDGE ARE ENCOUNTERING MID LEVEL
CONDITIONS FAVORABLE FOR ISOLATED SHOWER OR THUNDERSTORM
DEVELOPMENT. A BROAD DISTURBANCE CURRENTLY OVER IDAHO WILL
CROSS THE AREA TONIGHT AND MAY BRING A FEW LIGHT SHOWERS OR
THUNDERSTORMS WITH IT AS IT PROGRESSES TO THE EAST. KEPT SCHC POPS
IN FOR AREAS WEST OF BILLINGS WHERE TERRAIN WILL HELP CONVECTIVE
DEVELOPMENT...BUT LEFT AREAS TO THE EAST DRY TONIGHT GIVEN
WESTERLY FLOW ALOFT AND SUBSIDENCE UNDER THE RIDGE. TEMPERATURES
WILL BE WARM OVERNIGHT WITH 50S PREVALENT AND A FEW LOWER 60S NOT
OUT OF THE QUESTION.

PACIFIC STORM SYSTEM WILL SHIFT INTO THE AREA THURSDAY AFTERNOON.
AHEAD OF THIS SYSTEM EXPECT TEMPERATURES TO WARM INTO THE 80S WEST
AND INTO THE LOWER 90S OVER EASTERN AREAS. LOOKS LIKE A DECENT
AMOUNT OF MOISTURE FOR THIS SYSTEM TO WORK WITH AS IT CROSSES THE
AREA WITH PRECIPITABLE WATER VALUES AROUND AN INCH. HOWEVER THE
ENERGY WITH THE SYSTEM WILL SPLIT AS IT MOVES OVER MONTANA WITH
THE CORE OF THE SYSTEM SHIFTING OVER NORTHERN CALIFORNIA WHILE THE
PARENT TROF SLIDES ACROSS SOUTHERN CANADA. THIS SPLIT WILL LIMIT
PRECIPITATION POTENTIAL. BEST CHANCES FOR PRECIPITATION WILL BE
FROM LATE THURSDAY AFTERNOON INTO FRIDAY MORNING ACROSS THE AREA.
THUNDERSTORMS THURSDAY EVENING WILL HAVE SOME DECENT CAPE VALUES
TO WORK WITH. BRIEF HEAVY RAIN AND GUSTY WINDS WILL BE THE MAIN
THREAT WITH THESE STORMS. LINGERING INSTABILITY UNDER UNSTABLE
NORTHWEST FLOW WILL KEEP A SLIGHT CHANCE FOR SHOWERS GOING THROUGH
THE DAY FRIDAY BUT THIS LOOKS LIKE JUST A QUICK SHOT OF
PRECIPITATION POTENTIAL. TEMPERATURES WILL TREND COOLER FROM
FRIDAY INTO SUNDAY BEHIND THE SYSTEM AS REINFORCING COOL AIR LEAKS
IN FROM THE NORTH...BUT TEMPERATURES WILL REMAIN NEAR SEASONAL
LEVELS AND NO SIGNIFICANT COLD PUNCH SHOWS UP IN THE MODELS OVER
THE NEXT SEVEN DAYS. CHAMBERS

.LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED...

A VERY NICE WEEKEND AHEAD AS MODELS REMAIN IN GOOD AGREEMENT
THROUGH THE WEEKEND WITH THE EXITING OF THE UPPER TROF AND
BUILDING A STRONG RIDGE BY MONDAY AND TUESDAY. MODELS ARE ALL
GETTING CONSISTENT WITH UPPER LEVEL ENERGY DUCTING UNDER THE RIDGE
AND DRIFTING FROM CALIFORNIA INTO NORTHERN WYOMING MONDAY INTO
TUESDAY AS WELL. HOWEVER SOME OF THE MODELS ARE PUSHING THIS
ENERGY FURTHER NORTH INTO NORTHERN MONTANA WHILE OTHERS HOLD IT
ALONG THE SOUTHERN STATE LINE. WITH THIS SYSTEM BEING UNDER THE
STRONG CONVECTIVE POTENTIAL WILL BE LIMITED BUT COULD STILL BE A
FOCUS FOR ISOLATED TO SCATTERED AFTERNOON/EVENING THUNDERSTORMS.
ALREADY HAVE LOW POPS OVER SOUTHERN AREAS TO COVER THIS AND WITH
UNCERTAINTY REGARDING THE TRACK AND STRENGTH OF THIS ENERGY OUT
THAT FAR ELECTED TO KEEP PRECIPITATION CHANCES THE SAME FOR NOW.
WILL KEEP AN EYE ON THIS SYSTEM FOR POSSIBLE INCREASES IN
PRECIPITATION CHANCES GOING FORWARD. GFS AND ECMWF HAVE COME INTO
BETTER AGREEMENT FOR THE LATE EXTENDED AND BEYOND...PUSHING A
STRONGER PACIFIC SYSTEM INTO THE AREA LATE NEXT WEEK. THIS SYSTEM
LOOKS LIKE IT MAY BE SUPPORTED BY A PINEAPPLE EXPRESS TYPE
MOISTURE FEED OFF THE PACIFIC WHICH WOULD BE A WET PATTERN FOR
THE NORTHERN ROCKIES. WITH MODELS TRENDING IN A MORE CONSISTENT
DIRECTION EXPECT LATE PERIOD PRECIPITATION CHANCES TO INCREASE
WITH SUBSEQUENT FORECASTS. CHAMBERS

&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL TONIGHT. ISOLATED SHOWERS AND
THUNDERSTORMS WILL MOVE INTO WESTERN AREAS LATE THIS
AFTERNOON WITH A DISTURBANCE...AND WILL SHIFT EAST THIS EVENING.
BEST CHANCES FOR A THUNDERSTORM WILL BE NEAR HIGHER TERRAIN...BUT
A FEW CELLS MAY MAKE IT INTO THE LOWER ELEVATIONS ALONG A ROUNDUP
TO BILLINGS TO ASHLAND LINE BEFORE DISSIPATING AFTER SUNSET. GUSTY
WINDS TO 40KTS CAN BE EXPECTED NEAR ANY STORMS ALONG WITH LOCAL
MVFR CONDITIONS. CHAMBERS

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 058/087 058/080 051/076 051/074 049/074 051/076 053/076
    12/T    42/T    10/U    00/U    00/U    00/U    01/U
LVM 054/085 051/078 044/077 044/077 043/075 045/077 048/076
    23/T    42/T    21/U    00/U    01/U    11/U    11/U
HDN 054/090 056/082 050/078 048/077 047/076 049/078 050/079
    12/T    42/T    10/U    00/U    00/U    00/U    01/U
MLS 056/091 058/082 051/076 047/076 047/076 050/076 052/077
    12/T    32/T    00/U    00/U    00/U    00/U    01/U
4BQ 055/094 058/082 050/077 047/075 045/075 048/075 049/076
    11/B    32/T    10/U    00/U    00/U    00/U    01/U
BHK 052/090 056/081 049/075 044/072 043/072 045/073 048/076
    12/T    32/T    10/U    00/U    00/U    00/U    01/U
SHR 056/091 055/079 048/076 046/075 044/073 045/074 047/076
    12/T    33/T    21/U    00/U    00/U    00/U    01/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


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